The present invention relates to compositions and methods for catalyzing and controlling the rate of olefin metathesis reactions. More particularly, the present invention relates to compositions and methods for catalyzing and controlling the rate of Ring Opening Metathesis Polymerization (ROMP) reactions and the molding of polymer articles using ROMP polymers.
The molding of thermoset polymers is a technologically important processing technique. In one version of this technique, a liquid monomer (e.g., an olefin) and a polymerization catalyst are mixed and poured, cast or injected into a mold. The polymerization proceeds (the article "cures") and on completion the molded part is removed from the mold for any post cure processing that is required. The polymerization reaction mixture may optionally contain added modifiers, fillers, reinforcements, pigments, etc.
To mold successfully, the reaction mixture must not cure so quickly that the liquid monomer/catalyst mixture polymerizes before the mixture can be introduced in to the mold. In addition, the mixture must not cure so quickly that it has polymerized before the mold is completely filled or before the catalyst has had time to completely dissolve. For convenience and expedient cycle time, it is also important that the catalyst activate within a reasonable time after the mold is filled.
The time during which the liquid monomer/catalyst mixture can be worked after the monomer and catalyst is mixed is called the "pot life" of the polymerization reaction mixture. The ability to control the "pot life" becomes even more important in the molding of large parts. The monomer/catalyst mixture may also be applied to articles as a coating, and in this case it is also important to be able to control the "pot life" of the mixture. Generally, it would be useful to be able to control the rate of reaction of catalyzed metathesis reactions including ROMP reactions.
Reaction Injection Molding ("RIM") has previously been used for the molding of polymer articles using a polymerization catalyst and olefin monomer (U.S. Pat. Nos. 4,400,340 and 4,943,621). In these previous processes, a metal (W or Mo) containing compound is dissolved in a first monomer stream and an alkyl aluminum compound is dissolved in a second monomer stream. The monomer streams are then mixed and the metal containing compound and the alkyl aluminum compound react to form an active catalyst which then catalyzes the polymerization reaction. In the previous processes, the alkyl aluminum compound stream may also include an inhibitor, usually a Lewis base, which inhibits the rate of formation of the catalyst; however, in these previous processes, once the catalyst is formed, the polymerization reaction is extremely fast and there is no method to control the rate of polymerization initiated by the active catalyst species.
Previously, there has been few methods for producing a mixture of active catalyst species and monomer and controlling the rate of polymerization of the mixture other than by controlling the temperature of the monomer or the mold. Such control would be useful, for example, to produce a catalyst/monomer mixture in which the catalyst is substantially deactivated at room temperature. This mixture may then be poured, cast, or injected into a mold and the polymerization may then be initiated by heating the mixture.
There therefore exists a need for an olefin metathesis catalyst system that can be used to catalyze olefin metathesis reactions and control the rate of the catalyzed metathesis reaction. There is also a need for an olefin metathesis catalyst system that can be used to control the pot life of a monomer/catalyst mixture in a ROMP reaction.